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LDAP is a standard, AD is Microsoft's (proprietary) implementation (and more). Wikipedia has a good article that delves into the specifics. I found this document with a very detailed evaluation of AD from an LDAP perspective.

Thanks for the links. The PDF document, while informative, seems to broadcast negative sentiment towards Microsoft. While I assume the factual statements are correct, I found the tone distracting and it made them sound less than objective. Just my 2 cents.
– Mark BennettJun 25 '12 at 5:37

7

Not really an exact answer. LDAP is a protocol to access directory server, while Microsoft AD is an implementation of directory server.
– Daniel BaktiarMar 1 '13 at 16:36

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@Mark: Anti-Microsoft sentiments are common in Europe and especially in Germany and this should be factored into your interpretation of the document.
– cdonnerMar 7 '13 at 14:53

@MarkBennett From my (very quick) reading it appears their conclusions were that LDAP had security issues and was being pushed by a political agenda which was profit rather than security driven. I think using the term 'negative tone' is an understatement but, yes, Wayne Werner that's why I also read the document!
– sijpkesAug 7 '15 at 0:03

Lightweight Directory Access Protocol or LDAP, is a standards based specification for interacting with directory data. Directory Services can implement support of LDAP to provide interoperability among 3rd party applications.

Active Directory is Microsoft's implementation of a directory service that, among other protocols, supports LDAP to query it's data.

While it supports LDAP, Active Directory provides a host of extensions and conveniences, such as password expiration and account lockout.

Directory Service is a software system that stores, organises, and provides access to information in a computer operating system's directory. In software engineering, a directory is a map between names and values. It allows the lookup of named values, similar to a dictionary.

Secondly,as one could imagine, different vendors implement all kinds of forms of directory service, which is harmful to multi-vendor interoperability.

Thirdly, so in the 1980s, the ITU and ISO came up with a set of standards - X.500, for directory services, initially to support the requirements of inter-carrier electronic messaging and network name lookup.

Fourthly, so based on this standard, Lightweight Directory Access Protocol, LDAP, is developed. It uses the TCP/IP stack and a string encoding scheme of the X.500 Directory Access Protocol (DAP), giving it more relevance on the Internet.

Lastly, based on this LDAP/X.500 stack, Microsoft implemented a modern directory service for Windows, originating from the X.500 directory, created for use in Exchange Server. And this implementation is called Active Directory.

So in a short summary, Active Directory is a directory services implemented by Microsoft, and it supports Lightweight Directory Access Protocol (LDAP).

Active Directory isn't just an implementation of LDAP by Microsoft, that is only a small part of what AD is. Active Directory is (in an overly simplified way) a service that provides LDAP based authentication with Kerberos based Authorization.

Of course their LDAP and Kerberos implementations in AD are not exactly 100% interoperable with other LDAP/Kerberos implementations...

Active directory is a directory service provider, where you can add new user to a directory, remove or modify, specify privilages, assign policy etc. Its just like a phone directory where every person have a unique contact number. Every thing in AD(Active Directory) are considered as Objects and every object is given a Unique ID.(similar to a unique contact number in a phone directory.

Ldap is a protocol specially designed for directory service providers. Windows server OS uses AD as a directory server, AIX which is a UNIX version by IBM uses Tivoli directory server. Both of them uses LDAP protocol for interacting with directory.

active directory is the directory service database to store the organizational based data,policy,authentication etc whereas ldap is the protocol used to talk to the directory service database that is ad or adam.

There's a problem in Microsoft's explanation. Quote: Microsoft provides the Active Directory Service Interfaces (ADSI) for developing client-side directory service applications. ADSI consists of a directory service model and a set of COM interfaces. These interfaces enable development of network directory service access applications. ADSI uses an LDAP provider to communicate with Active Directory. ADSI can also access Novell NetWare Directory Services. ADSI can communicate with various directory services by using their native providers. --------- NetWare as opposed to AD or to LDAP?
– pashuteAug 5 '15 at 16:54

Realistically, there are probably more differences than similarities between the two directory solutions. Microsoft’s AD is largely a directory for Windows users, devices, and applications. AD requires a Microsoft Domain Controller to be present and when it is, users are able to single sign-on to Windows resources that live within the domain structure.

LDAP, on the other hand, has largely worked outside of the Windows structure focusing on the Linux / Unix environment and with more technical applications. LDAP doesn’t have the same concepts of domains or single sign-on. LDAP is largely implemented with open source solutions and as a result has more flexibility than AD.

Another critical difference between LDAP and Active Directory is how AD and LDAP each approach device management. AD manages Windows devices through and Group Policy Objects (GPOs). A similar concept doesn’t exist within LDAP. Both LDAP and AD are highly different solutions and as a result many organization must leverage both to serve different purposes.

This is why there’s an obvious opportunity for innovation. Why leverage and manage two complete systems, when one system can effectively merge the two?

Thank you for your interest in this question.
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